Patients with Alzheimers often complain of an inability to find their way even in familiar surroundings. Many such patients suffer a deterioration of visual function by the loss of acuity, contrast sensitivity, and visual motion sensitivity. We are testing a large, community-based cohort of Alzheimer's patients in an attempt to determine whether their difficulties with spatial orientation might be the result of impaired visual motion processing. Our hypothesis is that focal cortical degeneration in extrastiate visual areas creates a specific incapacity to acces the orienting cues imbedded in the optic flow field.